This invention relates generally to orthodontic devices and, in particular, to fixed mandibular arch and maxillary arch expanders which are connected together to allow for forward posturing of the mandible on closure.
Orthodontists treating children often need to gain space in a child's mouth for unerupted mandibular incisors and to increase intercanine distance for narrow archforms, as well as to distilize mandibular first molars so that a total increase of archlength is available in the lower dental arch from first molar to first molar. Furthermore, the orthodontist may want to expand the palate correspondingly.
Mandibular and maxillary arch expanders are known in the art to expand and lengthen the mandibular and maxillary archlengths. The use of such arch expanders help avoid the need for tooth extraction of permanent teeth due to overcrowding. However, such mandibular arch expanders are rather bulky in design, impede tongue mobility, are uncomfortable to wear, and interfere with good oral hygiene. The devices must be substantial in design to resist torquing or leverage mechanics during chewing.
To facilitate corresponding enlargement of the maxillary and mandibular arches, telescoping mechanisms have been employed which encourage forward repositioning of the lower jaw as the patient closes into occlusion. Such devices are commonly referred to as Herbst appliances. Current Herbst appliances include a hollow tube and a rod which is telescopically received in the tube. The tube is connected to the maxillary arch expander and the rod is connected to the mandibular arch expander. Currently available Herbst-type expanders have an initial amount of mandibular advancement built into the appliance. This amount of advancement, however, is generally not sufficient to establish an acceptable skeletal and dental relationship between the upper and lower jaw. Thus, the appliance has to be reactivated every two to three months. This generally includes substituting progressively longer tubes or by adding sleeves of tubing to the rod, to effectively increase the length of the tube. As can be appreciated, this process is cumbersome and time consuming.